<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>数组中第 K 个独一无二的字符串</title>
</head>
<body>
  <script>
    function fn(arr, k) {
      var n = 0
      for (var i = 0; i < arr.length; i++) {
        if (arr.indexOf(arr[i]) === arr.lastIndexOf(arr[i])) {
          n++
          if (n == k) return arr[i]
        }
      }
      return ''
    }
    console.log(fn(['d', 'b', 'c', 'b', 'c', 'a'], 2))
  </script>
</body>
</html>